Updates Compute API v2 WADL with relevant info from the Dev Ref

Merge once the approach is acceptable
Moved the extra content about servers to the top of Compute API v2 page.

Change-Id: I2be668deb6f039208e76cc9e59e3c483a671ad4e
Merge "Updates Compute API v2 WADL with relevant info from the Dev Ref"